What
is a virus?
A virus is a microbe.
A microbe is a tiny one-celled living
organism, too small to be seen with just your eyes. Other types
of microbes are: bacteria, protozoa, and fungi. Some people call microbes
"germs".

Not all microbes
are bad... Many bacteria live with us all the time, and help us do amazing
things like make yogurt, pickles, cheese, and even break down some garbage.
Microbes are all around us. They exist on our skin, and on the skin
of fruit. http://www.microbeworld.org/htm/aboutmicro/microbes/types/bacteria.htm

How
does a virus infect you? Viruses are
everywhere but they need to get inside a human, an animal or a plant
to make them sick. In fact, they must invade a cell, called a host
cell, in order to grow and reproduce. Most can't survive long unless
they're in a living host. Once inside, though, they can spread and make
other people sick. Some can live awhile on something like a desk, or
doorknob so it's important for you to wash your hands
regularly so you don't become infected!
Viruses can enter us
through the nose, mouth or breaks in the skin.

Viruses
are made of a small collection of genetic material
(DNA or RNA) encased in a protective protein coat called a capsid. Take
a peek at what's
inside a virus...

Is
a virus ALIVE? There is some debate about this. However, most scientists
say they are not alive because they cannot grow or reproduce on their
own.
They need a host cell to multiply.

Then
what happens? Once
inside a host cell they follow these basic steps in order to fool the
host cell into making make copies of the virus that might then infect
living organisms. This is called the lytic cycle.

The
Lytic Cycle- or how a virus fools a host cell into making more
viruses

A
virus attaches to a host cell. (All viruses have some type of protein
on the outside coat that "recognizes" the proper host cell.)

Your body's Immune
System to the rescue!!!Your body has a defense against viruses. It
is called the Immune
System. If a virus makes it past your
tough skin, or the sticky mucus and little hairs called cilia lining
your breathing tube then this system takes over.

Here's how it works...The
immune system is an organization of different types of cells, tissues
and enzymes work together to identify and eliminate all invading substances
in your body. Each part of the immune system has it's own specialized
job.

White
blood cells are your main defense. They patrol your body. When they
come across an antigen, they produce
an antibody that only works to fight
against that particular antigen. Some antibodies destroy antigens while
others make it easier for white blood cells to destroy the antigen.

Trillions
and trillions of white blood cells gobble the enemy. Sometimes, though,
your body needs help from the medicines doctors give you.
One of these medicines is called a vaccine.
Learn about vaccines here.

There
are hundreds of different kinds of viruses, and theyre constantly
changing. You can't catch the same virus twice. The
immune system can remember the response later if the foreign substance
invades the body again, and it gets right to work.